STRASBOURG, France  - The European Court of Human Rights on Tuesday ruled that Ukraine's detention of former prime minister Yulia Tymoshenko was unlawful, in a decision the opposition leader's camp saw as a key step towards her release.

"The court considered that the detention had been arbitrary and unlawful during the entire period," the judges of the Strasbourg-based court said.

The European Union is mulling a trade and association accord with the ex-Soviet republic and has clearly said it wanted Kiev to release the charismatic Tymoshenko.

Her daughter described the court's decision as a "first victory" and her lawyer argued that her nemesis President Viktor Yanukovych now had no option but to release her.

The judges also found that "the lawfulness of her detention had not been properly reviewed" by the Ukrainian judiciary "and that she had no possibility to seek compensation for her unlawful deprivation of liberty."